Doi Koichiro, Otsuka Sho, Nakagawa Seiji
Annu Int Conf IEEE Eng Med Biol Soc. 2020 Jul;2020:3877-3880. doi: 10.1109/EMBC44109.2020.9176626.
Ultrasound can be clearly perceived by bone-conduction, and this "bone-conducted ultrasound (BCU)" can transmit speech information by using amplitude modulation (AM). Further, BCU can be perceived not only on the head but also on the distal parts of the body like the neck, trunk and arms. This "distantly-presented BCU" can be applied to the novel interface that can transmit sound information selectively to specific users who touches the vibrator. However, the ability to transmit sound information of distantly-presented BCU is unclear. First, to assess frequency discrimination ability, difference limens for frequency (DLFs) of the distantly-presented AM-BCU were measured with/without a low-pass masking noise that masked the self-demodulated components generated by the nonlinearity of biological tissues. DLFs comparable to that of air-conducted sounds were observed, whereas DLFs significantly increased above 1 kHz under the masking condition. These results suggest that practical frequency discrimination ability can be obtained even when BCUs were presented to distal body parts. Additionally, it is indicated that the demodulated components may contribute to transmitting frequency information above 1 kHz. Second, monosyllable articulation and word intelligibility tests were conducted in Japanese. The intelligibility and articulation at the neck were 55% and 38% respectively, whereas they decreased as the stimulus placement gets farther from the head. The results suggest the distantly-presented BCU device can be applied to transmission of speech information.
超声波能够通过骨传导被清晰感知，这种“骨传导超声（BCU）”可以利用调幅（AM）来传输语音信息。此外，BCU不仅能在头部被感知，还能在身体的远端部位如颈部、躯干和手臂被感知。这种“远距离呈现的BCU”可应用于一种新型界面，该界面能够将声音信息选择性地传输给触摸振动器的特定用户。然而，远距离呈现的BCU传输声音信息的能力尚不清楚。首先，为了评估频率辨别能力，在有/无低通掩蔽噪声的情况下测量了远距离呈现的调幅BCU的频率辨别阈（DLF），该掩蔽噪声会掩盖生物组织非线性产生的自解调成分。观察到DLF与气导声音的相当，而在掩蔽条件下，1kHz以上的DLF显著增加。这些结果表明，即使将BCU呈现给身体远端部位，也能获得实际的频率辨别能力。此外，表明解调成分可能有助于传输1kHz以上的频率信息。其次，用日语进行了单音节清晰度和单词可懂度测试。在颈部的可懂度和清晰度分别为55%和38%，而随着刺激部位离头部越来越远，它们会下降。结果表明，远距离呈现的BCU设备可应用于语音信息的传输。
